1. Field of the Invention
The invention relates to a lens, and particularly to a projection lens.
2. Description of the Related Art
A projection lens adapted to a projection apparatus may have high imaging quality. In general, a frame projected by the projection lens may satisfy multiple conditions such as low distortion aberration, high resolution, high contrast, and high uniformity, etc. Furthermore, for reducing a projection distance, the projection lens may have a wide viewing angle.
It needs to overcome multiple difficulties to design a projection lens which satisfies the above-mentioned conditions. For example, the distortion aberration is usually increased with the widening of the viewing angle, and this makes it difficult to correct the distortion aberration. Furthermore, for correcting the distortion aberration, more lenses may be used, and a length of the projection lens and a cost of the projection lens are increased.
In view of the above, it is important to design a projection lens having advantages of high imaging quality, wide viewing angle, compact size, and low cost.